Raman suppression in a high-power single-mode fiber oscillator using a chirped and tilted fiber Bragg grating

We propose the design of a high-power fiber oscillator with chirped and tilted fiber Bragg gratings (CTFBGs) to suppress the stimulated Raman scattering within the fiber cavity and in the delivery fibers. A high-power single-mode fiber oscillator system was constructed for demonstration. With a CTFBG inserted into the fiber cavity, obvious Raman suppression was observed and the output signal laser power increased by similar to 7%. With a CTFBG inserted between the oscillator and the delivery fibers, a maximum Raman suppression ratio of >20 dB was achieved, which implies a longer delivery distance for the same laser power level. By further improving the performance of CTFBGs, including lower inversion loss at signal wavelength, wider rejection bandwidth and deeper rejection depth, meanwhile optimizing the positions of CTFBGs, better Raman suppression could be obtained, which is significant for the further power scaling and delivery distance increasing of high-power fiber oscillators.